JP3438379B2 - Hydrocarbon adsorbent, method for producing the same, and exhaust gas purification catalyst - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrocarbon adsorbent used for cleaning exhaust gas of an internal combustion engine or the like and a method for producing the same.
It also relates to an exhaust gas purification catalyst using the hydrocarbon adsorbent.

[0002]

2. Description of the Related Art Generally, exhaust gas from an automobile engine or the like contains atmospheric pollutants such as HC (hydrocarbon), CO (carbon monoxide), NOx (nitrogen participant). An exhaust gas purifying device using an exhaust gas purifying catalyst is provided in the exhaust system such as, but the exhaust gas purifying catalyst has a sufficient exhaust gas purifying performance unless the temperature thereof exceeds an activation temperature (for example, 250 ° C.). Does not exert. Therefore, when the exhaust gas temperature is low immediately after the engine is started, there is a problem that air pollutants are discharged into the atmosphere. Particularly, immediately after the engine is started, the HC concentration in the exhaust gas is relatively high, so a relatively large amount of HC is discharged into the atmosphere.

In order to solve this, for example, an exhaust gas purifying apparatus has been proposed which is equipped with an electric heater that heats the exhaust gas purifying catalyst immediately after the engine is started to accelerate its temperature rise. However, in this case, there arises a problem that the exhaust gas purifying device or the exhaust system becomes large and complicated, and the electric system also becomes large.

Therefore, an exhaust gas purifying catalyst using a hydrocarbon adsorbent capable of adsorbing HC at low temperatures, for example, an exhaust gas purifying catalyst in which a noble metal catalyst having an exhaust gas purifying ability is carried on the hydrocarbon adsorbent is proposed. Has been done. In such an exhaust gas purifying catalyst, HC in the exhaust gas is adsorbed by the hydrocarbon adsorbent at a low temperature, and when the exhaust gas purifying catalyst reaches the activation temperature of the precious metal catalyst or higher, the adsorbed HC is It will be purified (oxidized / combusted) by the noble metal catalyst supported on the hydrocarbon adsorbent.

As described above, zeolite has been conventionally known as a hydrocarbon adsorbent capable of adsorbing HC in exhaust gas. Specifically, MFI type zeolite, FA
U-type zeolite or MOR-type zeolite is used.

[0006]

However, the conventional exhaust gas purifying catalyst using zeolite has the following problems. That is, in the exhaust gas purifying catalyst using MFI type zeolite, since the pore size of the pores having a substantially circular cross section is relatively small (for example, 6Å or less), low-grade HC having a relatively small molecular size can be adsorbed without any trouble. Aromatic HC with a relatively large molecular diameter
However, there is a problem in that it cannot be effectively adsorbed.

Further, FAU type zeolite or MOR
In a conventional exhaust gas purification catalyst using type zeolite, the pore size of the pores with a substantially circular cross section is relatively large.
(For example, 6 Å or more), HC can be effectively adsorbed at a low temperature regardless of the size of the molecular diameter, but its adsorption power (HC holding power) is relatively small, so the exhaust gas purification catalyst has an activation temperature Adsorbed H before rising to
There is a problem that C is separated from the exhaust gas purification catalyst.

Further, the conventional exhaust gas purifying catalyst using zeolite tends to have low heat resistance (thermal structural stability) or durability, and when used for purifying engine exhaust gas, heat deterioration occurs. There is a problem that it is easy to cause.

The present invention has been made in order to solve the above-mentioned conventional problems, and is capable of sufficiently adsorbing HC at a low temperature regardless of the size of the molecular diameter, and adsorbing H
It is an object of the present invention to obtain a hydrocarbon adsorbent or an exhaust gas purifying catalyst capable of retaining C with a high adsorption force. Furthermore, it is an object to obtain a hydrocarbon adsorbent or an exhaust gas purifying catalyst having high heat resistance (thermal structural stability). In addition, it aims at obtaining the manufacturing method which can manufacture the said hydrocarbon adsorbent easily.

[0010]

The first aspect of the present invention, which has been made to achieve the above object, is a hydrocarbon adsorbent, which is a β type in which a large number of pores having different vertical and horizontal pore sizes are formed. It is characterized by containing zeolite.

A second aspect of the present invention is characterized in that the hydrocarbon adsorbent according to the first aspect of the present invention contains MFI type zeolite in addition to the β type zeolite.

[0012] A third aspect of the present invention is a method for producing a hydrocarbon adsorbent according to the first aspect of the present invention, in which each material for producing β-type zeolite is mixed to form a material mixture,
What is characterized in that the material mixture is heated to a β-type zeolite crystal growth temperature at a heating rate in the range of 22 to 58 ° C. per hour, and then kept at that temperature for a predetermined period to obtain a hydrocarbon adsorbent. Is.

A fourth aspect of the present invention is characterized in that, in the method for producing a hydrocarbon adsorbent according to the third aspect of the present invention, the heating rate is within the range of 25 to 58 ° C. per hour. To do.

A fifth aspect of the present invention is characterized in that, in the method for producing a hydrocarbon adsorbent according to the fourth aspect of the present invention, the heating rate is within the range of 28 to 55 ° C. per hour. To do.

A sixth aspect of the present invention is the method for producing a hydrocarbon adsorbent according to any one of the third to fifth aspects of the present invention, wherein the temperature of the material mixture is raised before starting.
It is characterized in that seed crystals are added to the material mixture.

A seventh aspect of the present invention is a method for producing a hydrocarbon adsorbent according to the second aspect of the present invention, wherein each of the β-zeolite producing materials is mixed to form a material mixture,
The material mixture is heated to the β-type zeolite crystal growth temperature and then kept at the temperature for a predetermined period of time, and then the material mixture is heated to the MFI-type zeolite crystal growth temperature and then kept at the temperature for a predetermined time. It is characterized by obtaining a hydrocarbon adsorbent.

An eighth aspect of the present invention is, in the method for producing a hydrocarbon adsorbent according to the seventh aspect of the present invention, before starting to raise the β-zeolite crystal growth temperature of the above material mixture, It is characterized in that seed crystals are added to the material mixture.

A ninth aspect of the present invention is an exhaust gas purifying catalyst for an internal combustion engine, which is characterized by containing the hydrocarbon adsorbent according to the first or second aspect of the present invention. Is.

[0019]

According to the first aspect of the present invention, the cross section of the pores of the β-zeolite contained in the hydrocarbon adsorbent has a shape having different vertical and horizontal pore diameters, for example, a substantially oval shape, Therefore, since the dimension of the pores in the major axis direction is relatively large,
From low-molecular-weight HC to high-molecular-weight HC at low temperatures
It is possible to easily adsorb a wide range of HC. On the other hand, since the size of the pores in the minor axis direction is small, the force for holding the adsorbed HC (adsorption force) becomes strong, and the HC once adsorbed by the hydrocarbon adsorbent is It does not easily leave the hydrocarbon adsorbent.

According to the second aspect of the present invention, basically, the same action as that of the hydrocarbon adsorbent according to the first aspect of the present invention occurs. Furthermore, since the hydrocarbon adsorbent contains MFI-type zeolite having a relatively small pore size in addition to β-type zeolite, HC having a small molecular size can be more effectively adsorbed.

According to the third aspect of the present invention, the β-zeolite is mixed with the material mixture at a heating rate within the range of 22 to 58 ° C./hour, which is slower than the conventional heating rate (for example, 220 ° C./hour). By raising the temperature to the crystal growth temperature, a hydrocarbon adsorbent containing a β-type zeolite having a large particle size and high purity or high crystallinity can be prepared.

According to the fourth aspect of the present invention, basically the same operation as in the method for producing a hydrocarbon adsorbent according to the third aspect of the present invention occurs. Furthermore, the heating rate is set to 25
By setting the temperature within the range of 58 ° C, a hydrocarbon adsorbent having high adsorption performance (high adsorption amount) can be prepared.

According to the fifth aspect of the present invention, basically the same action as the method for producing a hydrocarbon adsorbent according to the fourth aspect of the present invention occurs. Further, the temperature rising rate is 28
By setting the temperature within the range of 55 ° C, a hydrocarbon adsorbent having higher adsorption performance can be prepared.

According to the sixth aspect of the present invention, basically, the same action as that of the hydrocarbon adsorbent according to any one of the third to fifth aspects of the present invention occurs. Furthermore, by adding seed crystals to the material mixture before starting to raise the temperature of the material mixture, the generation and growth of β-zeolite particles can be promoted, and the particle size can be further increased and the purity or crystallization can be achieved. It is possible to make a hydrocarbon adsorbent containing β-type zeolite with higher degree.

According to the seventh aspect of the present invention, a part of the material can be converted to β-type zeolite by raising the temperature of the material mixture to the β-type zeolite crystal growth temperature and maintaining the temperature. After that, by heating the mixture of the materials to the MFI-type zeolite crystal growth temperature and maintaining the temperature at that temperature, the rest of the material can be made into the MFI-type zeolite, so that the carbonization containing β-type zeolite and MFI-type zeolite A hydrogen adsorbent can be easily made.

According to the eighth aspect of the present invention, basically the same action as the method for producing a hydrocarbon adsorbent according to the seventh aspect of the present invention occurs. Furthermore, by adding a seed crystal to the material mixture before starting the temperature rise of the material mixture to the β-type zeolite crystal growth temperature, the generation and growth of β-type zeolite particles can be promoted and the particle size can be increased. big,
In addition, a hydrocarbon adsorbent containing β-type zeolite having high purity or crystallinity can be prepared.

According to the ninth aspect of the present invention, since the exhaust gas purifying catalyst contains the hydrocarbon adsorbent according to the first or second aspect of the present invention, the molecular size may be large or small at low temperature. HC can be effectively adsorbed, and the adsorbed HC can be retained with a high adsorbing power, so that the HC adsorbed on the exhaust gas purifying catalyst is reliably purified.

[0028]

EXAMPLES Examples of the present invention will be specifically described below. <First Embodiment> A hydrocarbon adsorbent according to the first embodiment of the present invention will be described below. The hydrocarbon adsorbent according to the first embodiment is characterized by containing or consisting of β-type zeolite in which a large number of pores having different vertical and horizontal pore sizes are formed.

In this β-type zeolite, a large number of pores having different vertical and horizontal pore diameters, that is, a number of pores having a slightly elongated cross section or opening having a major axis and a minor axis are formed. The shape of such pores satisfies at least the following conditions. (1) Pore diameter is larger than 5.0Å (preferably 6.0)
Å or less). (2) The ratio of the long diameter of the pores to the short diameter of the pores (pore long diameter / pore short diameter) is larger than 1.10 (preferably about 1.25). The pores of the β-type zeolite in the first embodiment typically have a short diameter of about 5.5Å and a long diameter of about 7.0Å.
And the ratio of the major axis of the pores to the minor axis of the pores is about 1.25.

Since the pores of the β-type zeolite have such characteristics, the hydrocarbon adsorbent containing the β-type zeolite or composed of the β-type zeolite has a small HC at a low temperature. It is possible to easily adsorb HC over a wide range from to a large molecular diameter HC. In other words, since the major axis of the pores is relatively large, it becomes easy for HC to enter the pores regardless of the size of the molecular diameter.
Is easily adsorbed. More specifically, from aromatic HC having a molecular diameter similar to that of benzene and toluene, straight chain lower HC or branched lower HC having a small molecular diameter to aromatic HC having a large molecular diameter of xylene or more are evenly distributed. It becomes possible to adsorb.

On the other hand, since the minor axis of the pores is relatively small, the HC adsorbed in the pores is less likely to come out of the pores, and the hydrocarbon adsorbent has a higher HC retention performance (retention power). Therefore, even if the temperature of the hydrocarbon adsorbent rises, the HC adsorbed on the hydrocarbon adsorbent is not easily desorbed.

On the other hand, in the zeolite conventionally used as a hydrocarbon adsorbent, as described in the section "Problems to be solved by the invention", due to its pore shape, There was a problem. That is, MFI
In the case where the major axis of the pores of type zeolite is 6 Å or less, the lower HC (C ₂ -C ₄ ) is the main object to be adsorbed, and the adsorption performance of aromatic HC is low. In addition, in the case of FAU type zeolite, MOR type zeolite or the like having a long diameter of 6 Å or more, aromatic HC is an adsorption target, and the cross-sectional shape of the pore is close to a circular shape, so the pore size is an adsorption target. Since it is too large relative to the molecular diameter of HC, the retention performance of HC is low. That is, HC adsorbed at a low temperature cannot be retained as the temperature rises and is easily released.

Table 1 shows the pore shapes of the β-type zeolite contained in the hydrocarbon adsorbent in the first embodiment and the FAU which has been generally used as a hydrocarbon adsorbent in the past.
The pore shapes of type zeolite, MOR type zeolite and MFI type zeolite are shown in comparison. Further, FIG. 1 shows the relationship between the pore shape of each of these zeolites and the molecular diameter of HC to be adsorbed.

[0034]

[Table 1]

As is apparent from FIG. 1, among various conventionally used zeolites, the FAU type zeolite or the MOR type zeolite has an excessively short minor axis even with respect to the molecular diameter of aromatic HC having a relatively large molecular diameter. Therefore, the once adsorbed HC is easily desorbed when the temperature rises. On the other hand, in the MFI-type zeolite, its major axis is smaller than the molecular diameter of aromatic HC, and therefore aromatic HC cannot be effectively adsorbed.

On the other hand, in the β-type zeolite, the molecular diameters of benzene, toluene and xylene, which are the main components of the aromatic HC in the exhaust gas, are located between the short diameter and the long diameter.
Therefore, aromatic HC and the like can be easily adsorbed at a low temperature, and H adsorbed at a temperature rise.
Do not easily remove C.

FIG. 2 shows the hydrocarbon adsorbent using the β-type zeolite according to the first embodiment and the hydrocarbon adsorbent using the MFI-type or FAU-type zeolite conventionally used as HC. A simulated exhaust gas flow test was conducted using a simulated exhaust gas containing propylene (C ₃ H ₆ ) or toluene (C ₇ H ₈ ), and the propylene adsorption amount of each hydrocarbon adsorbent, the toluene adsorption amount, and the toluene desorption characteristics The results of actual measurement of (release characteristics of adsorbed toluene), that is, toluene retention performance are shown.

In this simulated exhaust gas flow test, the HC adsorption amount of each hydrocarbon adsorbent and the toluene desorption characteristic are evaluated under the following conditions. (1) Hydrocarbon adsorbent sample Each hydrocarbon adsorbent sample was prepared by mixing the corresponding zeolite, hydrated alumina, and water at a ratio of 5: 1: 20 (g) to form a slurry. It is made by wash-coating a honeycomb carrier. Here, each of the zeolites is a commercially available product, and a zeolite having a Cayvan ratio of 30 is used (the same applies to FIGS. 3 and 4).

(2) Measurement conditions A simulated exhaust gas flow test was conducted using the simulated exhaust gas having the gas composition shown in FIG. 2 at a volume velocity SV of 100,000 h ^-1 . The adsorption amount is the value when the temperature is raised from 100 ° C to 300 ° C at a heating rate of 10 ° C / min for propylene, and 10 ° C / mi for toluene.
These are values (absolute values) when the temperature is raised from 50 ° C. to 200 ° C. at a heating rate of n, and all of these values are adsorption amounts (mg) per 15 ml of honeycomb capacity. Toluene desorption characteristics
(Toluene retention performance) is evaluated by the half temperature of toluene. The toluene half temperature is the temperature at which the amount of toluene adsorbed decreases to half with the desorption (release) of toluene when the hydrocarbon adsorbent that adsorbs toluene at low temperature is gradually heated. However, the higher the toluene half-life temperature, the higher the toluene retention performance (adsorption force) (toluene is less likely to be desorbed).

According to FIG. 2, the hydrocarbon adsorbent containing β-type zeolite according to the first embodiment is capable of adsorbing (a) aromatic HC to lower HC, and (b) adsorbing it. H
It can be seen that C has an excellent retention property and can retain 16 mg of toluene at 140 ° C., and thus has an extremely good adsorption performance. By the way, the amounts of toluene adsorbed by MFI-type zeolite and FAU-type zeolite at 140 ° C. are 4 mg and 8 mg, respectively.

FIGS. 3 and 4 show an exhaust gas purifying catalyst using a hydrocarbon adsorbent containing β-type zeolite according to the first embodiment, and a hydrocarbon adsorbent containing MFI-type, FAU-type or MOR-type zeolite. The results of actually measuring the HC adsorption rate with respect to the exhaust gas discharged from the engine of the actual vehicle in the new state (fresh state) are shown for the exhaust gas purifying catalyst using. The evaluation conditions in each of the above actual measurements are shown in FIGS. 3 and 4, respectively.

In the example shown in FIG. 3, the main catalyst portion is composed of an adsorbent, a promoter and a noble metal. On the other hand, FIG.
In the example shown in (1), the main catalyst portion is composed only of the adsorbent. Further, in FIG. 3 or FIG. 4, the evaluation result is shown by the adsorption rate, but the adsorption rate here is 0-in the FTPY1 mode until the purification by the direct coupling catalyst is started.
A purification rate of 38 seconds is used.

Here, the method for producing the main catalyst portion (1.6 L) of each exhaust gas purifying catalyst in FIGS. 3 and 4 is as follows. In both FIGS. 3 and 4, a commercially available three-way catalyst (abbreviated as TWC, Pt-Rh 1.6 g / L) = 0.6 was used as the direct coupling catalyst.
5L * 2 is used. (1) In the case of FIG. 3, the adsorbent, the hydrated alumina, and the water are 300: 60: 1000.
Mix at a ratio of (g) to make a slurry.
The honeycomb carrier is wash-coated with 0 g. After this,
A honeycomb carrier is impregnated with an aqueous cerium nitrate solution and an aqueous palladium nitrate solution, and 70 g of ceria (cerium oxide) and 10 g of palladium oxide are carried on the honeycomb carrier. (2) In the case of FIG. 4, the slurry is wash-coated on the honeycomb carrier in the same manner as in (1) above.

According to FIGS. 3 and 4, in the exhaust gas purifying catalyst using the β-type zeolite according to the first embodiment, compared with the conventional exhaust gas purifying catalyst using other zeolites,
It can be seen that the adsorption rate is significantly improved. Therefore, the pore shape of the β-type zeolite according to the first example is
It can be said that it greatly contributes to the improvement of the HC adsorption rate under actual vehicle conditions.

FIG. 5 shows the Y1 purification rate (exhaust gas purification rate in the low temperature state at the initial stage after engine startup) when the exhaust gas exhausted from the actual vehicle is purified by using each exhaust gas purification catalyst in FIG. The measured value is shown. here,
The Y1 purification rate is the first mode in the FTP mode which is the US standard test mode. Note that the Y1 purification rate, the Y2 purification rate that is the second mode, and the Y3 purification rate that is the third mode are combined to form the FTP mode. Also,
FIG. 6 shows the actual measurement value of the Y1 purification rate in a new state and the actual measurement value of the Y1 purification rate after aging for the exhaust gas purification catalyst containing the β-type zeolite according to the first example and the conventional exhaust gas purification catalyst. Show. According to FIGS. 5 and 6, there is no difference in the Y1 purification rate between the first embodiment and the conventional example as much as the adsorption amount (see FIG. 3). It is considered that this is because the method for supporting the precious metal involved in the purification (oxidation / combustion) of HC on the base material is not very suitable. Therefore, by improving the supporting method,
It is considered that the Y1 purification rate can be sufficiently increased.

7 (a) and 7 (b) respectively show the exhaust gas purification catalyst containing FAU type zeolite and the exhaust gas purification catalyst containing β type zeolite in the example shown in FIG. The change characteristics of the HC emission amount with time when the exhaust gas is purified, that is, the adsorption behavior of HC is shown. Figure 7
In (a) and (b), graphs G ₁ and G ₁ ′ are exhaust gas temperatures after (downstream) the exhaust gas purifying catalyst, and graphs G ₂ and
G ₂ ′ is the HC emission amount before (upstream) the exhaust gas purification catalyst, and graphs G ₃ and G ₃ ′ are HC emission amounts after (downstream) the exhaust gas purification catalyst.

As is clear from FIGS. 7 (a) and 7 (b), when an exhaust gas purifying catalyst containing β-type zeolite is used (see FIG.
(b)) is compared with the case where the exhaust gas purifying catalyst containing FAU type zeolite is used (Fig. 7 (a)) at the initial stage (generally 0 to 40se).
The amount of HC discharged in c) is small, which shows that the β-type zeolite according to the first example has extremely good HC adsorption performance and HC retention performance.

<Second Embodiment> A second embodiment of the method for producing a hydrocarbon adsorbent will be described below. The hydrocarbon adsorbent containing the β-type zeolite or consisting of the β-type zeolite according to the first embodiment is basically prepared by mixing the respective production materials of the β-type zeolite to form a material mixture, and the material mixture is conventionally used. It is manufactured by a method in which the temperature is raised to the β-type zeolite crystal growth temperature at a temperature increase rate that is considerably slower than that of the above-mentioned manufacturing method, and then the temperature is maintained for a predetermined period.

According to such a manufacturing method, the material mixture can be heated to the β-type zeolite crystal growth temperature at a temperature rising rate much slower than the conventional temperature rising rate (for example, 220 ° C./hour). It is possible to obtain a hydrocarbon adsorbent containing a β-type zeolite having a high purity and a high degree of purity or crystallinity. And since the β-type zeolite having such a large particle size and high purity or high crystallinity has high heat resistance (thermal structural stability), it has excellent heat resistance (thermal structural stability) and thermal degradation. A hydrocarbon adsorbent that is less likely to occur is obtained.

Next, a specific method for producing a hydrocarbon adsorbent containing β-type zeolite according to the present invention will be described. The outline of the conventional method for producing β-type zeolite was as follows (for example, , Japanese Patent Application Laid-Open No. 5-220403). Incidentally, in the exhaust gas purifying catalyst containing β-type zeolite disclosed in JP-A-5-220403,
The type zeolite is used for purifying NOx, and is completely different from the present invention in the object of the invention, the constitution of the invention, and the action and effect. That is, first, a silica source (for example, silica sol), an alumina source (for example, sodium aluminate), and a template (for example, TEAOH) are mixed to prepare a mixed gel body, and the mixed gel body is charged into an autoclave. The β-zeolite crystal growth temperature is maintained for a predetermined period of time to form a crystal by hydrothermal synthesis, and the crystal is washed with water and dried, and then residual organic matter is removed at a predetermined temperature to obtain a β-type zeolite. However, the β-type zeolite obtained by such a conventional production method has low thermal structural stability, and the HC adsorption performance after heat treatment is significantly deteriorated.
It has the drawback of (heat deterioration).

On the other hand, in the β-type zeolite production method (hydrocarbon adsorbent production method) according to the second embodiment, the β-type zeolite is produced, for example, by the method shown in FIG. The β-type zeolite production method according to the second embodiment focuses on the crystal nucleation stage before the β-type zeolite crystal growth temperature is reached in the hydrothermal synthesis step (heating process up to the β-type zeolite crystal growth temperature). During the thermal synthesis, (a) the crystal nucleation step (temperature rising time) is set to 2.0 hours or more (conventional 0.5 hour), and (b) the seed crystal (crystallization) was performed before the hydrothermal synthesis. The main feature is to add an accelerator). As a result, β-type zeolite having a large particle size and a high degree of purity or crystallinity can be obtained. The β-zeolite produced by such a manufacturing method has high thermal structural stability and deterioration of HC adsorption performance even after heat treatment (heat deterioration).
Does not occur.

Hereinafter, according to the flow chart shown in FIG. 8, the method for producing β-type zeolite according to the second embodiment will be described in comparison with the conventional production method disclosed in, for example, JP-A-5-220403. To explain.
First, the synthesis methods are compared. In the conventional manufacturing method, β
Type zeolite (for example, when Si / Al = 20) is synthesized by the following procedure. That is, 40 wt% of SiO ₂
% Silica sol 581.0 g (silica source), sodium aluminate 17.4 g (alumina source), 40 wt% TEAO
A mixed gel body is prepared by mixing 210.7 g of H, (template) and 48.0 g of water. Next, this mixed gel body was charged in a Teflon-lined stainless steel autoclave, and the mixed gel body in the autoclave was kept at room temperature.
Start heating and pressurization under natural pressure (up to 20 kg / cm ² ),
The temperature is raised to 150 ° C., the temperature is maintained for 6 days, and crystals are formed by hydrothermal synthesis. Further, this crystal is washed with water and dried, and residual organic matter is removed at a temperature of 550 ° C. to obtain β-type zeolite.

On the other hand, in the manufacturing method according to the second embodiment, as shown in FIG. 8, β-type zeolite is obtained by synthesizing by the following method (when Si / Al = 20). .
That is, first, 100.0 g of silica sol which is a silica source.
(For example, CATALOID Si-30), 4.28 g of aluminum sulfate which is an alumina source (aluminum source), and 105.2 g of TEAOH which is a template (manufactured by Aldrich; 40
wt%) and 0.66 g of NaCl as an alkali metal source and K
3.35 g of Cl is mixed with an appropriate amount of water to form a mixed gel body (gel).

Next, this mixed gel body was charged into a Teflon-lined stainless steel autoclave,
Heating and pressurization of the mixed gel body in the autoclave is started at room temperature and under natural pressure (up to 20 kg / cm ² ) and the temperature is raised to a predetermined temperature within the range of β-type zeolite crystal growth temperature of 135 to 150 ° C. Then, hydrothermal synthesis (hydrothermal treatment) is performed by maintaining the temperature for 4 to 6 days to produce a Na-type crystal. More specifically, the temperature of the mixed gel body is raised in a temperature raising pattern as shown in FIG. 9, for example.

Here, it is preferable that the time required for the mixed gel body to reach a predetermined temperature within the β-zeolite crystal growth temperature range of 135 to 150 ° C. is about 2 hours or more. The preferable range of the heating time or the heating rate will be described in detail later. On the other hand, in the conventional β-type zeolite production method, for example, a heating pattern as shown in FIG. 10 is used, and the heating time is usually set to about 0.5 hours.

Before the hydrothermal synthesis, 10 wt% of theoretical yield of β-type zeolite crystal is added to the mixed gel body as a seed crystal (crystallization accelerator). Thus, mixed gel body
By adding seed crystals to the mixed gel body before starting the temperature rise of the (material mixture), β-type zeolite particles are produced.
A β-type zeolite (hydrocarbon adsorbent) that can promote growth, has a large particle size, and has high purity or crystallinity and is excellent in heat resistance or thermal structural stability and does not cause thermal deterioration can be obtained. .

Then, the Na-type crystal is subjected to an ion exchange treatment to be transformed into an H-type crystal (proton-type crystal) to obtain a β-type zeolite excellent in adsorption performance, adsorbed material retention performance and heat resistance. obtain.

In the method for producing a hydrocarbon adsorbent (β-zeolite) according to the second embodiment, as described above, the temperature rising time to the β-zeolite crystal growth temperature is conventionally (generally 0.5 hours). The particle size is large by making the length longer than that, so that the β-type zeolite having high purity or high crystallinity is obtained, but showing the dependence of the particle size (crystallinity) on the temperature rising time, β-type zeolite A micrograph of the crystal structure (particle structure) of is shown in FIG. In FIG. 11, (A), (B), (C), and (D) show that the heating time to the β-type zeolite crystal growth temperature is 0.5 hours, 1.0 hours, and 2.0 hours, respectively. 3 shows the crystal structure of β-zeolite for 4.0 hours. As is clear from FIG. 11, until the heating time is 2.0 hours, the particle size is increased corresponding to the increase of the heating time (reduction of the heating rate), but the heating time is 2 hours. Almost no increase in particle size is observed even if it exceeds.

FIG. 12 shows the X-type zeolite prepared by the production method according to the second embodiment (this example) and the β-zeolite produced by the conventional production method (comparative example).
The result of having measured the crystallinity by a line diffraction (XRD) is shown. Both β-zeolites are evaluated as H-type crystals (the same applies to FIGS. 13 to 18 below). The β-type zeolite used in this example is a sample in which the temperature rising time up to the β-type zeolite crystal growth temperature was 2.0 hours. As is clear from FIG. 12, the β-type zeolite produced by the production method according to the second embodiment has a significantly higher degree of crystallinity (and thus heat resistance) than the β-type zeolite produced by the conventional production method. It's getting higher.

13 and 14, the temperature rise time from the room temperature (25 ° C.) to the β-type zeolite crystal growth temperature (135 ° C.), which is basically produced by the manufacturing method according to the second embodiment, is 1. Regarding several β-type zeolites which are different from each other within the range of 0 to 5.0 hours, however, in FIG. 14, the β-type zeolite (comparative example) produced by the conventional production method also has a temperature up to the β-type zeolite crystal growth temperature. In order to investigate the influence of the temperature rise time (crystal nucleus formation time) on heat resistance and adsorption performance, BE
The result of having measured T surface area and the toluene adsorption amount (evaluated by a rig) is shown. Basically, the larger the BET surface area, the higher the heat resistance (thermal structural stability), and the larger the toluene adsorption amount, the better the adsorption performance.

As is clear from FIGS. 13 and 14, for the new β-type zeolite, the BET surface area gradually decreased as the temperature rising time was lengthened to about 1.9 to 2.0 hours, while the BET surface area increased. When the warming time is 2.0 hours or more, the BET surface area becomes relatively high and almost constant. On the other hand, for the β-type zeolite after aging, B was increased as the heating time was lengthened up to about 1.9 to 2.0 hours.
While the ET surface area increases, when the temperature rising time is 2.0 hours or more, the BET surface area becomes relatively constant at a relatively high value (slightly lower than that of a new product). Therefore, BET
From the viewpoint of surface area, that is, heat resistance, it is appropriate that the temperature rising time is set to approximately 1.9 hours or longer, preferably 2.0 hours or longer.

Regarding the new β type zeolite,
The amount of toluene adsorbed is at a high level until the temperature rise time is approximately 4.0 hours, but the amount of adsorbed toluene tends to decrease when the time is 4.0 hours or more, and tends to decrease when the time is 4.3 hours or more.
Especially, it drops sharply after 5.0 hours. Therefore, from the viewpoint of the amount of adsorbed toluene, that is, the adsorption performance, the temperature rising time is generally 5.0 hours or less, preferably 4.3 hours or less,
More preferably, it is appropriate that the time is 4.0 hours or less.

That is, the temperature raising time is 1.9 to 5.0 hours, preferably 1.9 to 4.3 hours, and more preferably 2.0.
It means that it is appropriate to set it to 4.0 hours. Here, if each of the above heating times is converted into a heating rate, a heating time of 1.9 to 5.0 hours corresponds to a heating rate of 22 to 58 ° C./h, and a heating time of 1.9 to Temperature rising rate 25-58 ° C for 4.3 hours
/ H, the heating rate is 2.0 for 4.0 hours and the heating rate is 2
Corresponds to 8 to 55 ° C. Therefore, the heating rate is 22
It is appropriate to set the temperature within the range of to 58 ° C / h, preferably within the range of 25 to 58 ° C / h, and more preferably within the range of 28 to 55 ° C.

FIG. 15 shows β-type zeolite prepared by the manufacturing method according to the second embodiment (the present invention) and three kinds of β-type zeolite prepared under the manufacturing conditions (not shown) not according to the present invention. With respect to zeolites (Comparative Examples 1 to 3), in order to examine the heat resistance (thermal structural stability), heat treatment was performed at various heat treatment temperatures, and then the BET surface area was measured.

As is clear from FIG. 15, in Comparative Example 1 and Comparative Example 3 in which the seed crystal is not used, the purity or crystallinity of the particles (crystals) cannot be sufficiently increased, so that the heat resistance is higher than that of the present invention. Very inferior. Also, in Comparative Example 2 in which the seed crystal was used but the temperature rising time to the β-type zeolite crystal growth temperature was 0.5 hours, the heat resistance was inferior to that of the present invention. On the other hand, in this case, the heat treatment temperature is 9
Almost no deterioration is observed up to 00 ° C.

FIGS. 16 and 17 show the β-type zeolite corresponding to the present invention in FIG. 15 (this example) and the β-type zeolite corresponding to Comparative example 3 in FIG. 15 (comparative example), respectively.
In order to compare the adsorption performance at the rig level, the results of measuring the toluene adsorption amount and the adsorption toluene retention performance (toluene desorption characteristic) are shown.

In FIGS. 16 and 17, the amount of toluene adsorbed and the toluene retention performance (adsorbed HC release characteristic) are evaluated under the following conditions. (1) All sample zeolites have Si / Al = 20. Then, the zeolite, hydrated alumina and water are mixed 5: 1:
A slurry was prepared by mixing at a ratio of 20 (g) to make a slurry, and this slurry was wash-coated on a honeycomb carrier. (2) Measurement conditions A simulated exhaust gas flow test (gas concentrations are shown in the figure) was performed at a volume velocity SV of 100,000 / h. The adsorption amount is
It is the absolute value of the adsorption amount when the temperature is raised from 50 ° C to 200 ° C at 10 ° C / min. Further, the toluene retention performance is evaluated by the half temperature of toluene. As is clear from FIGS. 16 and 17, the β-type zeolite of the present example is significantly superior to the β-type zeolite of the comparative example in the toluene adsorption amount and the adsorbed toluene retention performance.

FIG. 18 shows the evaluation results when the β-type zeolite produced by the production method according to the second embodiment and the β-type zeolite produced by the conventional production method were used as an HC adsorbent in an actual vehicle. Show. Here, the evaluation result when only the adsorbent is used for the main catalyst portion is shown. The evaluation result is shown as the adsorption rate, but the adsorption rate here is
The purification rate in 0-38 sec in the FTPY1 mode before the purification by the direct coupling catalyst is started is used. However, the main catalyst part (1.6 L) was washed with a slurry obtained by mixing the adsorbent, AP, and water at a ratio of 300: 60: 1000 (g) on a honeycomb carrier to give 150 g / It carries L adsorbent. A commercially available TWC (three-way catalyst, Pt-Rh 1.
6 g / L) = 0.65 L * 2 is used. As is clear from FIG. 18, in the example of the present invention, the adsorption rate in the new state is slightly inferior to that of the comparative example, but after aging, this is reversed, and it is confirmed that the heat resistance is improved even in the result of the actual vehicle evaluation. There is.

<Third Embodiment> A third embodiment of the method for producing a hydrocarbon adsorbent will be described below. The hydrocarbon adsorbent produced by the production method according to the third embodiment is characterized in that it contains MFI-type zeolite in addition to the β-type zeolite according to the first embodiment. Since this hydrocarbon adsorbent contains MFI-type zeolite having a relatively small pore size in addition to the β-type zeolite described above, HC having a small molecular size, for example, lower linear HC or branched HC is more effective. Can be adsorbed on.

In the method for producing a hydrocarbon adsorbent according to the third embodiment, basically, each material for producing β-type zeolite is mixed to form a material mixture, and the material mixture is mixed with β-type zeolite crystals. After the temperature is raised to the growth temperature, the temperature is maintained for a predetermined period, and then the material mixture is mixed with MFI.
It is characterized in that the hydrocarbon adsorbent is obtained by raising the temperature to the type zeolite crystal growth temperature and then maintaining the temperature for a predetermined time. Then, a seed crystal is added to the material mixture before the temperature rise of the material mixture to the β-type zeolite crystal growth temperature is started.

According to this manufacturing method, the material mixture is mixed with β
By raising the temperature to the zeolite-type zeolite crystal growth temperature and maintaining the temperature at that temperature, a part of the material can be converted to β-type zeolite, and then heating the material mixture to the MFI-type zeolite crystal growth temperature Since the rest of the material can be made into MFI-type zeolite by holding it at 1, the hydrocarbon adsorbent containing β-type zeolite and MFI-type zeolite can be easily prepared.

Further, by adding a seed crystal to the material mixture before the temperature rise of the material mixture to the β-type zeolite crystal growth temperature is started, the generation and growth of β-type zeolite particles can be promoted, It is possible to produce a hydrocarbon adsorbent containing a β-type zeolite having a large particle size and high purity or high crystallinity, which is excellent in heat resistance (thermal structural stability) and is resistant to thermal deterioration.

By the way, in general, as a method of mixing different kinds of zeolites at the crystal level in order to adsorb many kinds of HC (as a result, a method of uniformly dispersing zeolites having different pore sizes), "oxygen 8 member A hydrothermal synthesis is performed by using a zeolite having a ring or a 12-membered ring as a seed crystal according to a synthesis method of a 10-membered MFI-type zeolite. " However, with regard to β-type zeolite having a 12-membered oxygen ring, such a method cannot obtain the intended mixed system of β-type zeolite and MFI-type zeolite, and almost all become amorphous and MFI-type zeolite, resulting in HC adsorption. The performance as an agent is extremely low.

Thus, in the method for producing a hydrocarbon adsorbent according to the third embodiment, attention is paid to the physical similarity between β-type zeolite and MFI-type zeolite or the starting material thereof, and the hydrothermal synthesis is promoted. Devise the temperature pattern (optimization)
By this, β-type zeolite and MFI-type zeolite can be mixed at the crystal level. And, β-type zeolite and MF produced by such a manufacturing method
By using zeolite that is a mixed system with I-type zeolite (hereinafter, this is referred to as β-MFI mixed zeolite) as a base material, it is possible to compare with the mixed system obtained by the conventional method or the case of physical mixing of both zeolites. As a result, a hydrocarbon adsorbent having a high HC adsorption rate and thus an exhaust gas purification catalyst can be obtained.

19 and 20 are a flowchart showing a method for producing a hydrocarbon adsorbent containing a β-MFI mixed zeolite according to the third embodiment (hereinafter, referred to as a production method of the present invention) and a conventional method, respectively. 2 is a flowchart showing a method for producing a hydrocarbon adsorbent containing a β-MFI mixed zeolite, or a method for producing the mixed hydrocarbon adsorbent (hereinafter referred to as a conventional method). The production method (synthesis method) of the above-mentioned hydrocarbon adsorbent by the conventional method is as follows. That is, as also shown in FIG. 20, while stirring a slurry made by mixing 3.5 g of aluminum sulfate, 6.2 g of sulfuric acid, and 60 ml of water at 6000 rpm, the slurry was mixed with FAU-type zeolite (Cayvan ratio). 80 g), and a liquid consisting of 69 g of water glass No. 3 and 45 ml of water,
26.3 g of sodium chloride, 7.5 g of TPAB and 2.8 of sulfuric acid
A liquid consisting of 5 g and 2.4 g of sodium hydroxide was simultaneously added at 10 ml / min and 20 ml / min, respectively, and stirring was continued for 2 minutes after the addition. The precursor thus obtained is charged into an autoclave and filled with nitrogen so as to have a pressure of 4 kg / cm ² . This to 160 ℃ in 160 minutes,
Further, the temperature is raised to 200 ° C. in 600 minutes for hydrothermal synthesis, the product is washed with water, dried and then calcined at 550 ° C. for 2 hours to obtain a Na-type composite zeolite. After this, ion exchange was carried out for 2 hours in a solution prepared by dissolving 10 times the amount of Al of the Na-type composite zeolite in 500 ml of pure water, followed by calcination at 500 ° C. × 2 h for H (proton) type. It is transformed into crystals to obtain a hydrocarbon adsorbent containing (or expected to contain) β-MFI mixed zeolite.

On the other hand, in the production method of the present invention, attention is paid to the similarity of the starting materials in the synthesis of the β-type zeolite and the MFI-type zeolite, and the synthesis is carried out according to the following formulation (when the Cayvan ratio is 80). That is, as shown in FIG. 19, 100.0 g of silica sol as a silica source and (CATA
LOID Si-30), 2.14 g of aluminum sulfate as an alumina source (aluminum source), and TEA as a template.
105.2 g OH (Aldrich; 40 wt%), NaCl 0.3
3g, KCl 1.68g and an appropriate amount of water are mixed to form a mixed gel body. To this mixed gel, β-type zeolite crystals with a theoretical yield of 10 wt% were added and charged into an autoclave, and as shown in FIG.
Pressurization was started (up to 20 kg / cm), the temperature was raised to 135 ° C. in 0.5 hours, and then the temperature was maintained for 10 hours.
Hydrothermal synthesis is carried out in a temperature pattern in which the temperature is raised to 0.5 ° C. in 0.5 hour and the temperature is maintained for 4 hours. The product is washed with water, dried and calcined at 550 ° C. for 2 hours to obtain a Na-type composite zeolite. After that, H is processed by the same method as the conventional method.
A hydrocarbon adsorbent containing β-MFI mixed zeolite is obtained by converting the (proton) type crystal.

FIGS. 22 and 23 show X-ray diffraction (in this example) carried out to examine the composition of the hydrocarbon adsorbent containing the β-MFI mixed zeolite prepared by the manufacturing method of the present invention. XRD) measurement data and β- produced by the conventional method
The XRD measurement data performed to investigate the composition of a hydrocarbon adsorbent (comparative example) which is considered to contain MFI mixed zeolite is shown. 24 and 25 show XRD data of β-type zeolite and XRD data of MFI-type zeolite, respectively.

Referring to FIG. 22 with reference to FIGS. 24 and 25, in the hydrocarbon adsorbent produced by the production method of the present invention, a peak of β-type zeolite and a peak of MFI-type zeolite were observed, and both zeolites were mixed. You can see that On the other hand, referring to FIG. 23 in light of FIGS. 24 and 25, in the hydrocarbon adsorbent prepared by the conventional method, M
Although the peak of FI-type zeolite is recognized, the peak of β-type zeolite is hardly recognized, and the peak is substantially M.
It can be seen that only FI type zeolite is present.

FIG. 26 and FIG. 27 are XRD carried out to examine the composition of another hydrocarbon adsorbent (this example) containing the β-MFI mixed zeolite prepared by the manufacturing method of the present invention. And the composition of a hydrocarbon adsorbent (comparative example) which is thought to contain another β-MFI mixed zeolite prepared by the conventional method.
The measurement data of RD is shown. Further, FIG. 28 shows XRD data of β-type zeolite.

Referring to FIG. 26 with reference to FIG. 28, in the hydrocarbon adsorbent produced by the production method of the present invention, both the β-type zeolite peak and the MFI-type zeolite peak are strong, and both zeolites are sufficiently formed. You can see that it is done. On the other hand, referring to FIG. 27 in light of FIG. 28, in the hydrocarbon adsorbent prepared by the conventional method, both the β-type zeolite peak and the MFI-type zeolite peak are weak, and both zeolites are sufficiently produced. You can see that not.

FIG. 29 shows the β-MFI according to the third embodiment.
Evaluation results of an exhaust gas purification catalyst using a hydrocarbon adsorbent containing a mixed zeolite in an actual vehicle were obtained using a hydrocarbon adsorbent that is considered to contain a β-MFI mixed zeolite manufactured by a conventional manufacturing method. It is shown in comparison with the case of the exhaust gas purifying catalyst and the case of the exhaust gas purifying catalyst using a physically simple mixture of β-type zeolite and MFI type zeolite. Here, the evaluation result when only the adsorbent is used for the main catalyst portion is shown. The evaluation results are shown as the adsorption rate, but the adsorption rate here is 0-38 sec in the FTPY1 mode before the purification by the direct coupling catalyst is started.
The purification rate of is used. However, the main catalyst part (1.6
L) is an adsorbent, hydrated alumina and water 300: 60: 1
The honeycomb was wash-coated with a slurry produced by mixing at a ratio of 000 (g), and the slurry was carried at 150 g / L. In addition, a commercially available TWC (three-way catalyst, Pt-
Rh 1.6 g / L) = 0.65 L * 2 is used.

As is apparent from FIG. 29, the exhaust gas purifying catalyst according to the third embodiment (this embodiment) has a higher adsorption rate than the two comparative examples. In addition, even an exhaust gas purification catalyst using a physically mixed β-type zeolite and MFI-type zeolite includes a β-MFI mixed-type zeolite produced by a conventional manufacturing method which is amorphous in nature. The adsorption rate is considerably higher than that of the exhaust gas purifying catalyst using a hydrocarbon adsorbent, which is considered to be lower than that of this example.

[0083]

EFFECTS OF THE INVENTION According to the first aspect of the present invention, in addition to HC having a small molecular diameter, HC having a large molecular diameter can be easily adsorbed, and the HC retention performance is improved. It is possible to effectively adsorb HC regardless of the size of the molecular diameter, and it is possible to retain the adsorbed HC with a high adsorption force at the time of temperature rise.

According to the second aspect of the present invention, basically the same effect as that of the hydrocarbon adsorbent according to the first aspect of the present invention can be obtained. Furthermore, the MF having a relatively small pore size
Since HC having a small molecular diameter is effectively adsorbed by the I-type zeolite, the adsorption performance is further enhanced.

According to the third aspect of the present invention, a hydrocarbon adsorbent containing a β-type zeolite having a large particle size and a high purity or a high degree of crystallinity can be prepared. It is possible to obtain a hydrocarbon adsorbent which is excellent in the property) and is less likely to undergo thermal deterioration.

According to the fourth aspect of the present invention, basically the same effect as that of the method for producing a hydrocarbon adsorbent according to the third aspect of the present invention can be obtained. In addition, the heating rate is set to 25
Since the temperature is in the range of to 58 ° C, a hydrocarbon adsorbent having high adsorption performance (high adsorption amount) can be prepared.

According to the fifth aspect of the present invention, basically the same effect as the method for producing a hydrocarbon adsorbent according to the fourth aspect of the present invention can be obtained. Furthermore, since the rate of temperature increase is more preferably within the range of 28 to 55 ° C. per hour, a hydrocarbon adsorbent having higher adsorption performance can be produced.

According to the sixth aspect of the present invention, basically, the same effect as that of the hydrocarbon adsorbent according to any one of the third to fifth aspects of the present invention can be obtained. Furthermore, since the seed crystals promote the generation and growth of β-type zeolite particles, the β-type zeolite with a larger particle size and higher purity or higher crystallinity contains more heat resistance (thermal structural stability). It is possible to produce a hydrocarbon adsorbent excellent in), which is less likely to undergo thermal deterioration.

According to the seventh aspect of the present invention, a hydrocarbon adsorbent containing β-type zeolite and MFI-type zeolite can be easily prepared.

According to the eighth aspect of the present invention, basically the same effect as the method for producing a hydrocarbon adsorbent according to the seventh aspect of the present invention can be obtained. Furthermore, since the seed crystals promote the generation and growth of β-type zeolite particles, they contain β-type zeolite with a large particle size and high purity or crystallinity, and have excellent heat resistance (thermal structural stability). In addition, a hydrocarbon adsorbent that does not easily undergo thermal deterioration can be produced.

According to the ninth aspect of the present invention, the exhaust gas purifying catalyst can effectively adsorb HC regardless of the size of the molecular diameter at a low temperature and retain the adsorbed HC with a high adsorption force. As a result, the HC adsorbed on the exhaust gas purification catalyst is surely purified, and the exhaust gas purification rate is increased. In particular, the exhaust gas purifying catalyst is the second aspect of the present invention.
When the hydrocarbon adsorbent according to the above aspect is contained, the purification rate of low-grade HC having a small molecular diameter is significantly increased.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a zeolite pore size and an HC molecular size.

FIG. 2 is a diagram showing HC adsorption performance of various zeolites.

FIG. 3 is a diagram showing an adsorption rate of an exhaust gas purification catalyst using various zeolites.

FIG. 4 is a diagram showing an adsorption rate of an exhaust gas purification catalyst using various zeolites.

FIG. 5 is a diagram showing Y1 purification rates of exhaust gas purification catalysts using various zeolites.

FIG. 6 is a diagram showing Y1 purification rates before and after aging of an exhaust gas purification catalyst using β-type zeolite according to the present example and an exhaust gas purification catalyst using a conventional zeolite.

FIGS. 7 (a) and 7 (b) are diagrams showing changes over time in HC emission amount and exhaust gas temperature of an exhaust gas purification apparatus using a hydrocarbon adsorbent containing zeolite, respectively.

FIG. 8 is a flowchart showing a method for producing β-type zeolite according to the present invention.

9 is a graph showing a temperature rise pattern in the method for producing β-type zeolite shown in FIG. 8.

FIG. 10 is a graph showing a temperature rise pattern in a conventional β-type zeolite production method.

FIG. 11 is an electron micrograph of β-type zeolite.

FIG. 12 is an XRD chart of β-zeolite produced by the production method according to the present invention and β-zeolite produced by the conventional production method.

FIG. 13 is a diagram showing characteristics of BET surface area and toluene adsorption amount with respect to heating time.

FIG. 14 is a diagram showing characteristics of BET surface area and toluene adsorption amount with respect to heating time.

FIG. 15 is a diagram showing heat resistance of various β-type zeolites.

FIG. 16 is a diagram showing heat deterioration characteristics of β-type zeolite produced by the production method according to the present invention and β-type zeolite produced by the conventional production method.

FIG. 17 is a diagram showing heat deterioration characteristics of β-type zeolite produced by the production method according to the present invention and β-type zeolite produced by the conventional production method.

FIG. 18 is a diagram showing adsorption rates of an exhaust gas purification catalyst using β-type zeolite produced by the production method according to the present invention and an exhaust gas purification catalyst using β-type zeolite produced by a conventional production method. is there.

FIG. 19 is a flowchart showing a method for producing a β-MFI mixed zeolite according to the present invention.

FIG. 20 is a flowchart showing a conventional method for producing a β-MFI mixed zeolite.

FIG. 21 is a graph showing a temperature rise pattern in the method for producing the β-MFI mixed zeolite shown in FIG.

FIG. 22 is a β- produced by the production method according to the present invention.
It is an XRD chart of MFI mixed system zeolite.

FIG. 23 is an XRD chart of β-MFI mixed zeolite prepared by a conventional manufacturing method.

FIG. 24 is an XRD chart of β-type zeolite.

FIG. 25 is an XRD chart of MFI-type zeolite.

FIG. 26 is an XRD chart of another β-MFI mixed zeolite produced by the production method according to the present invention.

FIG. 27 Another β produced by the conventional manufacturing method
-It is an XRD chart of MFI mixed system zeolite.

FIG. 28 is an XRD chart of β-type zeolite.

FIG. 29 is a β- produced by the production method according to the present invention.
It is a figure which shows the adsorption rate of the exhaust gas purification catalyst using the MFI mixed system zeolite in comparison with a comparative example.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F01N 3/10 B01D 53/36 104Z (72) Inventor Osamu Takayama Shinchi Fuchu-cho, Aki-gun, Hiroshima Prefecture 3-1 Mazda Co., Ltd. (56) References JP-A-61-281015 (JP, A) JP-A-6-321530 (JP, A) JP-A-9-500081 (JP, A) (58) Fields investigated (Int.Cl. ⁷⁾ , DB name) B01J 20/18 B01D 53/86 B01D 53/94 C01B 39/46 B01J 29/70 F01N 3/10

Claims (9)

(57) [Claims] 1. A hydrocarbon adsorbent comprising a β-type zeolite in which a large number of pores having different vertical and horizontal pore sizes are formed. 2. The hydrocarbon adsorbent according to claim 1, wherein the hydrocarbon adsorbent contains MFI type zeolite in addition to the β type zeolite. 3. A material mixture is prepared by mixing the β-zeolite producing materials, and the material mixture is heated at 22 to 58 ° C. per hour.
The hydrocarbon adsorbent according to claim 1, wherein the hydrocarbon adsorbent according to claim 1 is obtained by raising the temperature to the β-type zeolite crystal growth temperature at a temperature raising rate within the range Method of manufacturing agent. 4. The method for producing a hydrocarbon adsorbent according to claim 3, wherein the heating rate is within a range of 25 to 58 ° C. per hour. 5. The method for producing a hydrocarbon adsorbent according to claim 4, wherein the heating rate is within a range of 28 to 55 ° C. per hour. 6. The method for producing a hydrocarbon adsorbent according to any one of claims 3 to 5, wherein seed crystals are added to the material mixture before the temperature of the material mixture is started. A method for producing a hydrocarbon adsorbent, comprising: 7. A material mixture is prepared by mixing the materials for producing β-type zeolite, and the material mixture is heated to the β-type zeolite crystal growth temperature and then held at that temperature for a predetermined period of time.
Thereafter, the mixture of materials is heated to the MFI-type zeolite crystal growth temperature and then kept at this temperature for a predetermined time to obtain the hydrocarbon adsorbent according to claim 2. Method. 8. The method for producing a hydrocarbon adsorbent according to claim 7, wherein seed crystals are added to the material mixture before the temperature rise of the material mixture to the β-type zeolite crystal growth temperature is started. A method for producing a hydrocarbon adsorbent, comprising: 9. An exhaust gas purifying catalyst for an internal combustion engine, comprising the hydrocarbon adsorbent according to claim 1 or 2.